fix: transaction countries should be optional

The `Transaction` countries on the Admin shouldn't be required.

Relates to #280

apps/billing/migrations/0005_alter_transaction_vat_identification_country.py

@@ -0,0 +1,18 @@
+# Generated by Django 4.2.8 on 2024-03-12 11:02
+
+import django_countries.fields
+from django.db import migrations
+
+
+class Migration(migrations.Migration):
+    dependencies = [
+        ("billing", "0004_alter_transactionitem_description_and_more"),
+    ]
+
+    operations = [
+        migrations.AlterField(
+            model_name="transaction",
+            name="vat_identification_country",
+            field=django_countries.fields.CountryField(blank=True, max_length=255, null=True),
+        ),
+    ]

apps/billing/models.py

@@ -46,9 +46,9 @@ class Transaction(BaseModel):
     city = models.CharField(max_length=100, null=True, blank=True)
     postal_code = models.CharField(max_length=50, null=True, blank=True)
     state = models.CharField(max_length=50, null=True, blank=True)
-    country_code = CountryField(max_length=255, null=True)
+    country_code = CountryField(max_length=255, null=True, blank=True)
     vat_identification_number = models.CharField(max_length=20, null=True, blank=True)
-    vat_identification_country = CountryField(max_length=255, null=True)
+    vat_identification_country = CountryField(max_length=255, null=True, blank=True)
     total_amount_exclude_vat = models.DecimalField(max_digits=10, decimal_places=2)
     total_amount_include_vat = models.DecimalField(max_digits=10, decimal_places=2)
     currency = models.CharField(max_length=7, default="EUR")